Watch a ‘heart’ made from liquid gallium beat in an electric field

Gallium droplets beat like tiny hearts when activated by electricity and could one day be used to power robot muscles.

Xiaolin Wang at the University of Wollongong and his colleagues demonstrated this heartbeat effect by placing a drop of liquid gallium inside a circular electrode.

In their video, the gallium droplet initial rests against one side of the electrode, which is tipped at a slight angle. When an electric current is applied, the gallium starts reacting with the surrounding water to form gallium oxide.

Because gallium oxide has less surface tension than gallium, the spherical droplet starts to spread out like a pancake. This momentum propels it away from the side of the electrode.

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Once it loses contact with the electrode, the gallium oxide turns back into gallium and the droplet regains its spherical shape. Gravity then pulls it back into contact with the electrode.

Liquid metal

This cycle continues, making the gallium look like a beating heart as it repeatedly shapeshifts and bounces against the side of the electrode.

Wang’s team showed that the rate of this gallium “heartbeat” could be adjusted by changing the strength of the electric current. It’s the first time that a liquid metal has been made to pulse in a controlled fashion using electricity, he says.

The work was inspired by the movie Terminator 2, which features a shapeshifting robot called T-1000 made out of liquid metal, Wang says.

Pulsating gallium droplets might be useful for powering artificial muscles in soft, liquid-based robots, he says. “For example, they could be used to pump the robot’s muscles and propel it forward.”